<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>登录</title>
</head>
<style type="text/css">
    body{
        padding: 0;
        margin: 0;
    }
    .body_1{
        width: 1200px;
        margin: 0 auto;
        height: 800px;
    }
    .body_1 .mains{
        width: 600px;
        height: 400px;
        margin: 0 auto;
        margin-top: 200px;
    }
    .body_1 .mains .top{
        width: 600px;
        height: 100px;
        background-color: royalblue;
        text-align: center;
    }
    .body_1 .mains .top >span{
        font-family: 微软雅黑;
        font-size: 40px;
        color: white;
        line-height: 100px;
    }
    .body_1 .mains .center{
        width: 600px;
        height: 300px;
        background-color:  cornflowerblue;
        text-align: center;
    }
    .body_1 .mains .center .yonghu{
        padding-top: 30px;
    }
    .body_1 .mains .center .yonghu,.mima,.denglu{
        width: 600px;
        height: 50px;
        text-align: center;
        line-height: 50px;
        font-family: 微软雅黑;
        font-size: 20px;
        color: white;
    }
    .body_1 .mains .center .denglu >input{
        width: 100px;
        height: 25px;
        border-radius: 4px;
    }
</style>
<body>
<form action="login.html" method="get">
    <div class="body_1">
        <div class="mains">
            <div class="top">
                <span>图书管理系统</span>
            </div>
            <div class="center">
                <div class="yonghu">
                    用户名 <input type="text">
                </div>
                <div class="mima">
                    密&nbsp;&nbsp;&nbsp;码 <input type="password">
                </div>
                <div class="denglu">
                    <input type="submit" value="登录">
                </div>
            </div>
        </div>
    </div>
</form>
</body>
</html>